The recent social demand for energy saving has created a need for automobiles to have low heat build-up properties (fuel economy) and abrasion resistance. This demand has also created a need for rubber compositions for tires to have fuel economy and abrasion resistance. In this context, white fillers such as silica or aluminum hydroxide are widely used in rubber compositions for tires to improve fuel economy.
White fillers such as silica and finely divided aluminum hydroxide have problems of excessive compound viscosity, poor extrusion processability, and poor sheeting processability because these particles tend to be bound to form aggregates during kneading. Therefore, there has been a need to improve the processability of white filler-containing rubber compositions.
The prior art has reported techniques for improving the processability of rubber compositions containing white fillers such as silica. For example, Patent Literature 1 discloses an amide compound for use as a processing aid to improve dispersion of silica in rubber compositions. The amide compound has a polar end that is weakly chemically reactive with silica and a non-polar end that is weakly chemically reactive with elastic polymers. This document also describes techniques including adding the amide compound to rubber compositions containing silica. Moreover, Patent Literatures 2 to 5 disclose techniques including adding a fatty acid monoethanolamide or fatty acid diethanolamide to rubber compositions containing white fillers such as silica.